In certain riveting situations, such as some applications in the aircraft industry, it is believed desirable to have high-strength fasteners that are slightly larger than the hole in which they are to be installed, such that the rivets have to be forced into the hole with high interference. For example, titanium rivets may be forced into softer aluminum. This approach guarantees a tight fit with a rivet having high shear strength capabilities. Also, inserting the rivet, cold-works the material through which the rivet is inserted, thereby hardening and strengthening it.
When working with regular riveting tools, the clamping force is not sufficient to support the workpiece enough to drive a rivet in the hole with high interference. As a result, aircraft manufacturing has developed other techniques such as to employ rivets of special shapes or special coatings, or use vibrational inserters, and reduce the interference in the rivet installation. With such approaches, the cost of installation is increased, but yet maximum strength is not achieved.
In some manufacturing operations, holes through workpieces are pre-drilled, and riveting is later performed after a separate positioning and clamping operation. This requires accurate alignment and coordination between the drilling and riveting operations, and increases expense. It is desirable that the rivet hole be drilled immediately preceding the installation of the rivet using the same fixturing and clamping arrangement. This approach is more accurate and more efficient.
It is particularly desirable to have an efficient installation tool for a recently developed rivet of the type disclosed in U.S. Pat. No. 4,688,317, issued to the same assignee as the present invention. With that rivet, a portion of an upset head is partially sheared from the head and flattened against the workpiece. This technique provides tension on the rivet shank to maintain a tight joint.